1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor integrated circuit device, and a semiconductor integrated circuit device manufactured by the method. More particularly, the present invention relates to a method of manufacturing a semiconductor integrated circuit device that can be more stably operated, and a semiconductor integrated circuit device manufactured by the method.
2. Description of the Related Art
MOS (Metal-Oxide Semiconductor) devices are increasingly miniaturized in response to the desire to increase the integration of semiconductor devices. Channel lengths are reduced to the deep sub-micron level in order to increase an operating speed and current drive capability of the device.
With a reduction in the channel length, depletion regions of a source electrode and a drain electrode penetrate into a channel area, thereby shortening an effective channel length. As a result, a threshold voltage is reduced, thereby leading to a loss of gate controllability in an MOS transistor, which is called a short channel effect. In particular, with the effective channel length reduced, hot carriers are generated, thereby lowering the current drivability and the refresh characteristics, and ultimately deteriorating a reliability of semiconductor devices.
To avoid hot carrier effect and improve the reliability of semiconductor devices, after a gate formation process, a reoxidation process may be performed. However, when the reoxidation process is performed, a thickness of a gate insulating layer may be increased due to a bird's beak phenomenon, resulting in a reduction in the operating speed of a semiconductor device. Thus, the reoxidation process is not suitably employed in the manufacture of fast operating semiconductor devices.
Meanwhile, various types of transistors are present in a semiconductor device unit of a semiconductor integrated circuit device. These transistors require reliability, a fast operating speed, current driving capability, etc., but must satisfy more important characteristics according to their own requirements. For example, some transistors require higher reliability, whereas some transistors require a faster operating speed.
Accordingly, when all transistors are subjected to a reoxidation process to remove a hot carrier effect, characteristic requirements of some transistors may be deteriorated.